1. Measuring the angle of a component. 2. Checking the sloping angle of a vee-block. 3. Measuring the angle of a cone or taper gauges. 4. Precise angular settings for machining operations.

1. AutoCollimator
Angle Dekkor
Presentation Prepared by
Prof. Naman M. Dave
Assistant Prof. (Mechanical Dept.)
Gandhinagar Institute of Technology
Mechanical measurement and metrology
Prof. Naman M. Dave

2. Mechanical measurement and metrology
Prof. Naman M. Dave
Please refer this file just as
reference material. More
concentration should on class
room work and text book
methodology.

3. INTRODUCTION
Collimation
Mechanical measurement and metrology
Prof. Naman M. Dave

4. Principle of AutoCollimator
The two main principles used in an
autocollimator are
(a) the projection and the refraction
of a parallel beam of light by a
lens, and
(b) the change in direction of a
reflected angle on a plane
reflecting surface with change
in angle of incidence.

5. AutoCollimator
Mechanical measurement and metrology
Prof. Naman M. Dave

6. AutoCollimator

7. Mechanical measurement and metrology
Prof. Naman M. Dave

8. Mechanical measurement and metrology
Prof. Naman M. Dave
• These can be adjusted with the micrometer until they straddle the reflected image
of the cross wires. A scale is provided in the eye piece which directly gives the tilt
of the reflector.
• The micrometer has 60 divisions and the micrometer moves the setting wires
through 1/2 minute per revolution. Thus each division on the microscope drum
corresponds to 0.5 sec. of arc.
• The micrometer microscope system provided measures the deflection of the image
and hence the angle of the work piece.
• Autocollimators are capable of reading upto 0.1 seconds and may be used over
distances upto 30 meters. But their range of measurements is small and hence they
are used more as comparators than as absolute measuring devices.
• They are particularly useful for checking surface flatness and alignment over large
distances. For efficient working of autocollimators the work piece surface must be
highly polished and should be optically flat.
• Slip gauges are sometimes wrung on the surface of the work piece to help
reflection.
• Readings of the autocollimeter are sometimes subject to fluctuations due to air
currents between the autocollimeter and the target mirror.
• The fluctuations are more pronounced for larger distances between the instrument
and mirror.
• Flatness and reflectivity of the target mirror also affect the accuracy of the
readings.

9. Mechanical measurement and metrology
Prof. Naman M. Dave
• An illuminated Cross Line Target reticule placed at the focus of the Objective
collimating lens is projected after reflection from a beam splitter.
• A Plane reflector placed normal to the optical axis of parallel beam in front of the
objective Lens returns the beam along their original paths.
• A portion of the returned light passes straight through the beam splitter and the
return image of the target cross line is viewed through an Eyepiece.
• The Eyepiece is provided with a measuring Graticule. The reflected Image of the
Target cross line is brought to focus in the plane of the Eyepiece graticule and
exactly coincident with its intersection.
• If the reflector is tilted through a small angle the reflected light beam will be
brought to focus in the plane of the Eyepiece Reticule but linearly displaced by an
amount 2Tan θ x f.
• Linear displacement of the reticule image in the plane of the eyepiece is therefore
directly proportional to reflector tilt and can be measured by an eyepiece reticule or
an optical micrometer system.
• The focal length determines basic sensitivity and angular measuring range. The
longer the focal length the larger is the linear displacement for a given reflector tilt.
• The maximum working distance is the separation between reflector and
autocollimator and is governed by the effective diameter of the objective lens. At
long working distances the angular measuring range of the instrument reduces.
Large size reflectors are required atleast equal to the diameter of the Objective lens
to have better image contrast.
Description from 2nd reference material

10. AutoCollimator

11. AutoCollimator

12. AutoCollimator
Applications:
1. Checking of an internal right angle.
2. Comparative measurement using master angles.
3. Measuring straightness and flatness of the surfaces.
4. Assessment of squareness and parallelism of
component.
5. For machine tool adjustment setting.

13. Mechanical measurement and metrology
Prof. Naman M. Dave

14. Mechanical measurement and metrology
Prof. Naman M. Dave

15. Mechanical measurement and metrology
Prof. Naman M. Dave

16. Mechanical measurement and metrology
Prof. Naman M. Dave

17. Mechanical measurement and metrology
Prof. Naman M. Dave

18. Mechanical measurement and metrology
Prof. Naman M. Dave

19. Angle Dekkor

20. Angle Dekkor

21. Angle Dekkor

22. Mechanical measurement and metrology
Prof. Naman M. Dave
• The reflected image of the illuminated scale shown in Fig. and the
fixed datum line intersect each other at right angles
• The reading on the illuminated image represents the deviation from
one axis at 90" to the optical axis. The change in the angular
position of the surface is shown by the variation in the position of
the point of intersection of the two scale on the fixed datum scale.
• Readings from scale can be read directly upto I minute without the
use of a micrometer.
• The optical system of the dekkor shown in Fig. is enclosed in a
tube mounted on an
• adjustable bracket and the whole system is mounted on a flat
reflective base.
• Angle dekkor can be used in conjunction with angle gauges for
measuring angles, setting of jobs for machining and measuring
angles of cones. The principle of measurement consists of
comparing the reading obtained with a polished reflector or slip
gauges in contact with the work piece and a zero reading obtained
from an angle gauge block set up.

23. Mechanical measurement and metrology
Prof. Naman M. Dave
• Fig. shows schematically the method for finding the angle of a
work piece using the dekkor.
• First a set of angle gauge blocks with an angle close to the angle to
be measured is placed on the surface plate and the reflected image
for the angle set is observed in the eyepiece. The dekkor can then
be set such that zero reading is obtained on the illuminated scale.
• The angle gauge set is then replaced by the workpiece on which a
slip gauge is attached to serve as a reflector.
• The difference between the angle of the workpiece and the angle of
the gauge block set, if any, appears as the difference between the
position of the reflected scale on the datum line as error as shown
in Fig.
• Angle dekkor is not a precision measuring instrument compared to
an auto collimator but serves as a simple general purpose
instrument in the shop. It has the advantage of giving readings
directly without the use of a vernier. The angle difference between
the reference position and test position can be read to an accuracy
of 10 minute which is good enough for general workshop use.

24. Angle Dekkor
Applications:
1.Measuring the angle of a component.
2.Checking the sloping angle of a vee-
block.
3.Measuring the angle of a cone or taper
gauges.
4.Precise angular settings for machining
operations.